Monitoring of azathioprine-induced immunosuppression with thiopurine methyltransferase activity in kidney transplant recipients.

Thiopurine methyltransferase (TPMT), one of the enzymes involved in azathioprine metabolism, exhibits a wide range of activity in the normal population. We prospectively evaluated the monitoring of erythrocyte TPMT activity (using a radiochemical method) in kidney transplant recipients with regard to the efficacy of azathioprine. Three patterns in TPMT activity variation were observed.

[Homozygote deficiency of thiopurine methyltransferase. A contraindication to the use of azathioprine in kidney transplantation].

Azathioprine-induced myelosuppression is the most important side effect observed in kidney transplantation. We report a case of severe neutropenia after kidney transplantation due to a thiopurine methyltransferase deficiency. This cause of azathioprine-induced myelotoxicity is rare, but its infectious consequences may be severe.